Hot wire switch for directional signals and the like



Nov. 19, 1963 J. H. JAIDINGER 3,111,566

HOT WIRE SWITCH FOR DIRECTIONAL SIGNALS AND THE LIKE Filed May 27, 1960 2 Sheets-Sheet 1 IZVVQNTOR. 5 BY I B Aw,

2 Sheets-Sheet 2 J. H. JAIDINGER v INVENTOR: Z 5 Z I BY BM,%AA1Q\4I Bo 7 8 I HOT WIRE SWITCH FOR DIRECTIONAL SIGNALS AND THE LIKE Nov. 19, 1963 Filed May 27, 1960 United States Patent Ofiice 351M566 Patented Nov. 19, 1963 3,111,566 HGT WIRE SWITCH FUR DIRECTIONAL SIGNALS AND THE LIKE John H. Jaidinger, 1921 W. Hubbard St, Chicago, Ill. Filed May 27, 1960, Ser. No. 32,203 14 Claims. (Cl. 200-413) The present invention relates to switches, especially snap and flasher switches, and in particular, to an improved snap acting flasher switch for use in conjunction with automobile directional signals and the like.

Directional signals are standard equipment on almost all current model automobiles and incorporate, in most instances, an automatic switch for alternately energizing and de-energizing a selected tail light and front parking light of the automobile to cause the same to flash on and off, thereby indicating to other drivers the intention of the user to turn his vehicle in a given direction. To serve this purpose effectively, the light should flash on and off at a predetermined frequency, the on and off times should preferably be nearly equal, and the electrical components should have long service life.

The object of the present invention is the provision of an improved switch of particular economy and compactness fully satisfying the stated requirements.

Another object of the invention is to provide an improved snap acting switch embodying a flexible fulcrum member, a movable contact blade pivoted on the fulcrum member and over-center link means for actuating the blade and flexing the fulcrum member, thereby to enhance the snap action of the switch, decrease blade throw, and mitigate variable contact pressure and sticking of the blade.

An additional object of the invention is to provide an improved movable contact blade and blade mounting distinguished by rein-forcing means for the blade and an interlocking connection between the blade and its. supporting fulcrum member.

It is also an object of the invention to provide an improved mounting stack assembly characterized by a single fastener, whereby the length and the cost of the switch may be appreciably reduced.

A further object of the invention is the provision of an improved flasher switch including an actuator blade, a simple wire or rod subject to thermal elongation upon flow therethrough of electric current for controlling the actuator blade, and a strut operatively interposed between the wire and the blade for relieving the blade of endwise thrust that would otherwise be exerted thereon by the wire, whereby the switch components are not adversely affected by the presence and association therewith of the wire.

A still further object of the invention is the provision of an improved switch combining all of the above stated structural and operational features, and comprising a particularly compact and economical switch structure having long service life and consistent operational characteristics throughout its life.

Other objects and advantages of the invention will become apparent in the following detailed description.

Now, in order to acquaint those skilled in the art with the manner of making and using my improved switch, I shall describe, in connection with the accompanying drawings, preferred embodiments of the switch and preferred manners of making and using the same.

In the drawings, wherein like reference numerals indicate like parts:

FIGURE 1 is a side elevation of the right-hand side of a preferred embodiment of the switch of the invention;

FIGURE 2 is a side elevation of the left-hand side of the switch;

FIGURE 3 is a plan view of the switch;

FIGURE 4 is a fragmentary longitudinal section, on a somewhat enlarged scale, of the preferred embodiment of the switch;

FIGURE 5 is a fragmentary longitudinal sectional view depicting the mounting of the movable contact blade on its fulcrum support;

FIGURE 6 is a fragmentary plan view of the components illustrated in FIGURE 5;

FIGURE 7 is a plan view of the flexible blade member of the preferred embodiment of the switch, which blade member embodies therein one stationary blade, the fulorum portion or legs and the actuator blade of the switch;

FIGURES is a view similar to FIGURE 3 of a second embodiment of the switch; and

FIGURE 9 is a view similar to FIGURE 4 of the second embodiment of the switch.

Referring now to the drawings, the switch of the invention is shown as comprising, in general, a mounting stack 2%, a pair of spaced stationary blades 21 and 22 projecting a short distance from the stack, a movable actuator blade or portion 23 projecting outwardly from the stack in the same direction as but appreciably beyond the blades 21 and 22, a fulcrum portion 24 projecting from the stack into a window area in the actuator 25 and beyond the blades 21 and 22, a movable contact blade 25 fulcrumed on the portion 24, a toggle link 26 operatively connecting the movable blades 23 and 2-5, a flasher opera-ting wire 27, a strut 2:8 operatively connecting the wire and the actuator blade, and a terminal 29 to which the wire is connected.

In the illustrated construction, the lower one of the two stationary blades, ie, the blade .21, comprises a stationary contact and is formed integrally with a rearwardly extending plug-in type of terminal member 30. The terminal member 30 is offset laterally from, and disposed in a plane perpendicular to, the blade 21, and the two are joined by a mounting portion 31 coplanar with the blade and forming part of the stack. Adjacent the outer end thereof, the blade 21 is provided on its upper surface with a contact '32, which may suitably be formed of palladium or a gold and platinum alloy for long service life.

t'Ihe terminal 229 is disposed below the blade 21 and includes a mounting portion 33 spaced from the mounting portion '31 of the blade 21 by one or more insulating washers 3d, the said mounting portions and washers constituting part of the stack. Formed integrally with the portion 33 is a rearwardly extending plug-in terminal member 35 similar to the member 3%) which is disposed in a plane at right angles to the plane of the member 30. These two members are adapted to be inserted in a complementary socket (not shown) for connection to an electric supply source, and are also adapted to have pressfitted thereon a terminal board (not shown) adapted for association with a switch enclosing can (not shown), whereby the switch may be sealed within a can for conventional reasons. The terminal 29' also includes a transverse projection 36 extending to the side of the stack opposite the terminal member 30, to which projection the flasher wire 27 is connected.

While the actuator blade 23, the fulcrum portion 24 and the upper stationary blade 22 may, if desired, be formed separately of one another, it is one object of this invention to form the same from a unitary piece of flexible stock, preferably a sheet of nickel-silver alloy or Phosphor bronze. A unitary piece of this flexible sheet metal, i.e., a flexible blade member, is suitably stampedout to define, as shown in FIGURE 7, a mounting portion 33 forming part of the stack, a pairof spaced parallel actuator legs 39 extending outwardly from the opposite sides of the mounting portion, a transverse outer end portion 44} joining the actuator legs at their outer ends and defining a window between the legs 39 and the portions 38 and 40, a pair of spaced parallel fulcrum legs 41 spaced respectively from said actuator legs and disposed within the defined window, and a central portion bent upon itself to form the upper blade 22 of the switch. In the disclosed embodiment of the switch, the upper blade 22 comprises simply a stop, and may therefore be formed integrally with the actuator blade, i.e., the actuator legs 39 and end portion 40, and the fulcrum legs 41. In embodiments requiring a second stationary contact, the projection would be replaced by a separate contact blade similar to the blade 21 with its associated terminal 30. Adjacent their outer ends, the fulcrum legs 41 are bent upwardly at an inclination of about 45 degrees for a purpose to be described. Also for a purpose to be described, the actuator legs 39 are bent or prestressed in an upward direction.

In the stack 20, the mounting portion 38 of the flexible blade member is spaced upwardly from the lower stationary blade 21 by one or more of the insulating washers 34, and one or more of the washers are disposed above this member. The several mounting portions 31, 3'3 and 38, and the several washers 34 are provided centrally thereof with a hole of non-circular or polygonal configuration, most simply a square hole, the several holes being aligned. Fitted within the aligned holes is a tube 42 of insulating material, suitably nylon, which has an outer surface configuration complementary to the configuration of the holes, i.e., a square tube in the disclosed embodiment. The tube 42 is of a height slightly less than the height of the stack, yet of suflicient height to fit within the holes in at least the portions 31, 3-3 and 38 to maintain these portions against relative rotation. Extended through the tube is a single fastener 43, such as a rivet, having head means 44 associated therewith for bearing engagement against the opposite sides of the stack. Preferably, the head means 44 comprise cup washers which are prestressed in assembly of the stack so as to impose a tensile load on the body of the fastener and a compressive load on the stack. By virtue of the square holes and the square tube 42, only a single fastener is required to hold the components thus far described in properly assembled relation, and to retain the same against relative rotation. The length of the stack is thereby considerably shortened.,fand the cost of the switch significantly reduced by the savings in material and in assembly consequent upon elimination of the necessity for a plurality of fasteners.

The stack assembly is of particular importance in maintaining a selected frequency of operation of the switch, since it constitutes the reaction point of the switch blade supporting and actuating components, or in other words, the base of the switch. To maintain a fixed mounting, I employ perfectly plane mounting portions 31, 3 3 and 38. The washers 34 are preferably formed of glass melamine because of the insulating qualities and physical stability of the material, even when subjected to wide temperature and pressure variations. The square tube is formed of nylon also for purposes of stability, and is of a length no greater than the height of the stack so as not to interfere with the function of the cup washers 44. The washers 44 in turn serve to'rnaint-ain a uniform compressive force on the stack, thereby to maintain the predetermined fixed relationship of the mounting portions 31, 33 and 38.

The movable contact blade 25, which is preferably formed of brass, may also be formed of Phosphor bronze or nickel-silver, comprises a generally planar body portion of a width no greater than the spacing between the fulcrum legs 41. At the inner end thereof, the blade carries on its lower surface a contact 45 formed preferably of the same material as, and adapted for contacting engagement with, the stationary contact 32. Intermediate its ends, the body is provided at its opposite sides with upstanding flanges 46 which serve to rigidify the blade and provide means for mounting the blade on the fulcrum legs 41. At the outer ends thereof, the fulcrum legs include inwardly extending transverse portions 47 which, as previously stated, are inclined to the plane of the legs and are also inclined to the plane of the blade 25. Consequently, as shown in FIGURE 5, each transverse portion 47 defines an inwardly facing knife-like fulcrum edge 48 on which the respective flange 46 of the blade is adapted to seat. For purposes of inter-locking the blade and its fulcrum support, each of the transverse portions 47 has a longitudinal slot '49 therein and each of the flanges 46 at the outer edge thereof is provided with a shallow arcuate recess 50. In assembly, the flanges are positioned within the slots 49 and the fulcrum edges 48 are positioned in the recesses 50, whereby the blade is retained on the fulcrum and pivotally mounted on knife-edge fulcrum supports.

The blade 25 is slotted longitudinally from just outwardly of the contact 45 to its outer end thereby to accommodate the link 26. A hole is formed in the body of the blade and a similar hole is provided in the end potrion 40 of the actuator blade, within which holes the opposite ends of the link are pivotally mounted.

The link 26 primarily serves two purposes: (1) to hold the blade 25 on the fulcrum or fulcrum legs and (2) to comprise a toggle actuating link between the actuator blade 23, i.e., the legs 39 and portion 40, and the movable contact blade 25. In the embodiment of the invention shown in FIGURES 1 to 7, the link comprises a tension coil spring stretched between the two blades under predetermined tensile load, whereby the same not only performs the two functions stated but also comprises a toggle spring for actuating the movable contact blade 25 with a snap action. In the embodiment of the invention shown in FIGURES 8 and 9', the link comprises simply a rigid rod or wire 26a extending between the two blades and pivotally mounted in the holes therein. In this latter embodiment, the flexible fulcrum legs 41 comprise the spring means of the toggle mecha-.

nism, and for this purpose are provided intermediate their ends with vertically bowed or crimped portions 410. As will be appreciated, the portions 41a accommodate longitudinal flexing of the legs, as well as the lateral flexing accommodated by the flat or planar fulcrum legs of the embodiment of the invention shown in FIGURES 1 to 7.

In use of either embodiment of the invention, movement imparted to the actuator blade generally perpendicular to the outer end portion 49 thereof will result in actuation of the switch blade 25 with a snap action. With the contacts engaged as depicted in the drawings, upward movement of the actuator blade will result in upward movement of the outer end of the link 26 until the link moves upwardly over-center relative to the fulcrum edges 43. Thereupon, the toggle spring (either the coil tension spring 26 or the compression spring defined by the bowed legs 41a) will move the movable contact blade upwardly to the opposite side of center with a snap action. Simultaneously, the outer ends of the fulcrum legs will be snapped in the opposite direction, i.e., downwardly, because of their transverse flexibility. Due to this latter movement, the snap action is compounded to insure a quick snap-over of the movable contact blade, and to accommodate decrease of the are of movement of the contact carrying end of the blade. Moreover, the force of the fulcrum legs 41 is available to maintain pressure on the contact blade in the direction of contact en gagement until the moment of snap-over, so as to mitigate decrease in contact pressure as the link 26 moves toward dead center, minimize arcing and eliminate sticking of the contacts. At the moment of snap-over, all spring components act substantially simultaneously to insure the desired movement of the contact blade. Upon movement of the actuator blade in the downward direction, the movable contact blade is snapped back into engagement with the stationary blade 21, and the fulcrum legs are snapped upwardly. Thus, the center point of the toggle assembly,

i.e., the fulcrum edge 43, moves up and down to accommodate significant movement of the actuator blade without requiring other than a short excursion of the contact carrying. end of theblade 25.

As thus far described, the switch of the invention comprises an improved snap switch well suited for a wide variety of uses. In these uses, the actuator blade may have no initial stress or it may be prestressed in either the upward or downward direction normally to maintain the contacts open or closed, respectively, as may be desired for a particular purpose. For the purpose now to be described, I prestress the actuator blade in the upward direction, by appropriate bending of the actuator :legs 39, normally to bias the contact 45 away from the contact 32 and into engagement with the stop 22.

In the embodiments herein illustrated, the switch of the invention is intended to be automatically operative to open and close a circuit at a predetermined frequency or rate, i.e., to comprise a flasher control switch. For this purpose, the switch is operated by means of the wire 27 which is normally of such length as to hold the portion 4b of the actuator blade 23 down to close thecontacts 32 and 45, and which is subject to thermal expansion upon passage of electric current therethrough to release the actuator blade for movement of the contact blade 25 to disengaged or open position. To this end, the wire is connected to the terminal 29 and via the actuator and movable contact blade to the movable contact 45. Thus, when current is first supplied to the switch it will flow via the terminal 3% contact blade 2-1, contacts 32 and 45, blades 25 and 23, and strut 28 through the wire and to the terminal 29. The wire is preferably relatively soft stainless steel wire of high tensile strength having a large coefficient of thermal elongation and sufiicient resistance to current flow to produce significant heating and thus significant elongation in the [wire upon passage of electric current therethrough. Consequently, upon occurrence of current flow, the wire commences to heat and elongate, thereby releasing the actuator blade 23 for movement in the direction in which it was prestressed, i.e., upwardly. When the blade 23 moves the link 26 overcenter, the contacts become disengaged and the circuit is opened. The wire then cools and contracts, causing the blade 23 to be moved downwardly to effect re-engagement of the contacts, whereupon the wire 27 is again connected in the circuit and the described cycle of operation will be automatically repeated. The switch thus. automatically opens and closes the circuit.

In experimentation with the switching arrangement described, many factors were found to affect the frequency or rate of operation of the switch. Because of the heat produced by the wire 27, or possibly because of other factors, the stack would appear to vary dimensionally, which would cause extreme variation in the periodicity of switching and/or result in inoperativeness. Use of dimensionally stable components, especially the melamine glass insulating washers, and the prestressed cup washers have solved all problems in this respect. Also, thermal variations and/or variable [force exertions appear to cause distortion of the movable contact blade and consequent maloperation of the switch. Adoption of the reinforc-ing flanges 4 6 eliminated this problem. For similar reasons, it appeared that the fulcrum legs, the movable contact blade and/or the means for mounting the blade on the legs produced another source of malfunction. Adoption of the improved blade mount of this invention has solved all such problems. Yet, despite all of these improvements, the switch would not perform consistently with the wire 27 directly connected to the actuator blade 23. In retrospect, it appears that the wire imposed an endwise stress on the blade which, under the variable thermal conditions encountered in use, created a variable loading condition adversely affecting switch operation. This latter problem has been cured by the strut 28 of this invention.

The prime purpose of the strut 28 is to form an operative connection between the wire and the actuator blade 23 such that the blade is entirely relieved of endwise thrust, is actuated by force exerted substantially perpendicular thereto and yet does not nesessitate disposition of the operating wire or thorn al unit at right angles to the blade. More particularly, it is a purpose of the strut 23 to accommodate disposition of the thermal Wire generally parallel to the blade so that a relatively long length of wire may be employed without increasing the transverse or lateral dimensions of the switch. In its preferred embodiment, as shown herein, the strut comprises an elongate metal strap having a depending leg 51 and 52, respectively, at each end thereof. The leg 51 at the inner end of the strap has a rearwardly opening generally horizontal slot 53 at its lower end by means of which the strut is pivotally mounted adjacent the stack on the flexible blade member in the space between one leg 39 and the adjacent leg 41 of the mamber. From this position, the strut extends outwardly toward the end of the switch and laterally toward the center thereof. At the outer end of the strut, the leg 52 extends downwardly into engagement with the upper surface of the outer end portion 4% of the flexible member, and the said leg is pro vided with a reduced extension 54 projecting through a diagonal slot 55 provided in the said portion 40. The arrangement of the slot and the leg 52 is such that the leg engages the upper surface of the portion 4b centrally thereof and the extension 54 is spaced from the bottom or inner end of the slot 55 so as to impose no endwise load on the blade or the actuator legs 39 thereof. Below the blade, the wire 27 is secured to the lower end of the leg extension 54. In its normal condition, the wire causes the strut to pivot downwardly about its mounting point to bear downwardly on the portion 49 of the flexible blade member centrally thereof without imposing an endwise stress on the member, thereby to cause engagement of the contacts. Upon heating and elongation of the wire, the actuator portion of the flexible member readily moves the portion at and the outer end of the strut upwardly to effect disengagement of the contacts. Due primarily to its presence, and more particularly to the provision thereby of an effective lever arm for the wire and the diagonal extension of the same, the strut 28 accommodates a particularly long thermally expansible operator wire or rod for the switch, thereby to facilitate automatic control of the switch. With this strut, and the other improvements specified, I have provided a flasher switch of completely consistent operation from the mo ment of energization to the moment of de-energization, throughout a long service life.

From the foregoing, it is believed apparent that I have provided an improved snap switch and an improved flasher switch satisfying the requirements of the art and attaining in an economical, convenient and practical man ner all of the objects of this invention.

While I have shown and described what I regard to be the preferred embodiments of my invention, it is to be appreciated that various changes, rearrangements and modifications may be made therein without departing from the scope of the invention, as defined by the appended claims.

I claim:

1. In a switch, a mounting stack, a pair of spaced stationary blades projecting a short distance outwardly from the stack, a flexible fulcrum portion projecting outwardly from said stack beyond said stationary blades, said portion being bifurcated from inwardly of the outer ends of said stationary blades to its outer end and defining a fulcrum adjacent the outer end thereof, a short movable contact blade pivoted on said fulcrum and projecting inwardly therefrom between the bifurcations of said portion into the space between the said stationary blades and proximate to said stack, a movable actuator blade projecting outwardly from said stack beyond said fulcrum, said actuator blade having a window therein coextensive with the bifurcations of said fulcrum portion and terminating in outwardly spaced relation to said movable contact blade, said movable contact blade having a pivot surface on a portion thereof spaced from said fulcrum and said actuator blade including a pivot surface on a portion thereof opposed to the said portion of said movable contact blade, and a link extending between and pivotally mounted at its opposite ends on the said pivot surfaces on said movable contact blade and said actuator blade, said link retaining said movable contact blade on said fulcrum, said actuator blade being movable to swing said link to opposite sides of a position centered on said fulcrum, said link moving said movable contact blade toward the stationary blade at the side of said fulcrum to which the link is moved and by the intermediary of said movable contact blade flexing said fulcrum portion in the direction away from said link.

2. In a switch, a mounting stack, a pair of spaced stationary blades projecting a short distance outwardly from the stack, a flexible blade member projecting outwardly from said stack beyond said stationary blades, said member including a pair of spaced parallel flexible fulcrum legs extending outwardly from said stack beyond said stationary blades, a pair of flexible actuator legs spaced laterally outward from the respective ones of said fulcrum legs and a transverse outer end portion joining said actuator legs outwardly of said fulcrum legs, said fulcrum legs defining a fulcrum adjacent the outer ends thereof, a short movable contact blade pivoted on said fulcrum and projecting inwardly therefrom between said fulcrum legs into the space between the said stationary blades and proximate to said stack, said movable contact blade having a pivot surface on a portion thereof spaced from said fulcrum and said transverse end portion of said flexible member including a pivot surface on a portion thereof opposed to the said portion of said movable contact blade, and a link extending between and pivotally mounted at its opposite ends on the said pivot surf-aces on said movable contact blade and said transverse end portion of said flexible member, said link retaining said movable blade on said fulcrum, said actuator legs being movable to swing said link to opposite sides of a position centered on said fulcrum, said link moving said movable contact blade toward the stationary blade at the side of said fulcrum to which the link is moved and by the intermediary of said movable contact blade flexing said fulcrum legs in the direction away from said link.

3. In a switch, a mounting stack, a pair of spaced stationary blades projecting a short distance outwardly from said stack, a fulcrum portion projecting outwardly from said stack beyond said stationary blades, said portion being bifurcated from inwardly of the outer ends of said stationary blades to its outer end and defining a fulcrum adjacent the outer end thereof, a short movable contact blade pivoted on said fulcrum and projecting inwardly therefrom between the bifurcations of said portion into the space between the said stationary blades and proximate, to said stack, the bifurcations of said fulcrum portion -in cluding at their outer ends transverse portions defining said fulcrum, each of said transverse portions having a longitudinal slot therein, said movable contact blade including at its opposite sides upstanding flanges fitting within the respective ones of said slots, the edges of said flanges engaging said transverse portions having recesses therein receiving said transverse portions and effectively interlocking said movable contact blade and said fulcrum portion, a movable actuator blade projecting outwardly from said stack beyond said fulcrum, said actuator blade having a window therein coextensive with the bifurcations of said fulcrum portion and terminating in outwardly spaced relation to said movable contact blade, said movable contact blade having a pivot surface on a portion thereof spaced from said fulcrum and said actuator blade including a pivot surface on a portion thereof opposed to the said portion of said movable contact blade, and a link extending between and pivotally mounted at its opposite ends on the said pivot surfaces on said movable contact blade and said actuator blade, said link retaining said movable contact blade on said fulcrum with the said flanges thereof engaged in said slots.

4. In a switch, a mounting stack, a pair of spaced stationary blades projecting a short distance outwardly from the stack, a flexible blade member projecting outwardly from said stack beyond said stationary blades, said member including a pair of spaced parallel flexible fulcrum legs extending outwardly from said stack beyond said stationary blades, a pair of flexible actuator legs spaced laterally outward from respective ones of said fulcrum legs and an outer end portion joining said actuator legs outwardly of said fulcrum legs, said fulcrum legs including at their outer ends transverse portions defining a fulcrum, each of said transverse portions having a longitudinal slot therein, a short movable contact blade pivoted on said fulcrum and projecting inwardly therefrom between said fulcrum legs into the space between said stationary blades and proximate to said stack, said movable contact blade including at its opposite sides upstanding flanges fitting within the respective ones of said slots, the edges of said flanges engaging said transverse portions having recesses therein receiving said transverse portions and effectively interlocking said movable contact blade and said fulcrum legs, said movable contact blade having a pivot surface on a portion thereof spaced from said fulcrum and said outer end portion of said flexible member including a pivot surf-ace on a portion thereof opposed to the said portion of said movable contact blade, and a link extending between and pivotally mounted at its opposite ends on the said pivot surfaces on said movable contact blade and said actuator blade, said link retaining said movable contact blade on said fulcrum.

5. A switch comprising a flexible blade member having a mounting end with a polygonal hole therethrough, a pair of spaced parallel fulcrum legs extending outwardly from said mounting end, a pair of spaced parallel actuator legs extending outwardly from said mounting end to opposite sides of said fulcrum legs and an outer end portion joining said actuator legs outwardly of said fulcrum legs, at least one stationary contact blade having a mounting end with a polygonal hole theretbrough aligned with the hole in said blade member and a contact end extending outwardly a short distance from said mounting end and terminating intermediate the ends of said fulcrum legs, insulation between the mounting ends of said stationary contact blade and said flexible blade and forming therewith a mounting stack, a polygonal tube of insulating material disposed within said stack and intimately engaging in said holes in said blade and said member, said tube being of a height less than said stack, a single fastener passing through said tube and having head means at its opposite ends pressing against the opposite sides of the stack, at least one of said head means comprising a cup Washer imposing a tensile load on said fastener and a compressive load on said stack, said fulcrum legs including transverse portions adjacent their outer ends tilted relative to said legs and defining a knife-like fulcrum edge, a movable contact blade mounted between said fulcrum legs and extending proximate to said stack and the said blade end of said stationary contact blade, said movable contact blade comprising a generally planar member having upstanding flanges intermediate the ends and adjacent the opposite sides thereof, said transverse portions of said fulcrum legs being opposed to said flanges and having longitudinally extending slots therein, said flanges being received within said slots and having recesses in the ends thereof engaging about the said knife-like fulcrum edge, whereby the movable contact blade is pivotally mounted on said fulcrum edge and effectively interlocked with said fulcrum legs, said movable cont-act blade having a pivot surface on a portion thereof spaced from said fulcrum and said outer end portion of said flexible member including a pivot surface on a portion thereof opposed to the said portion of said movable contact blade, and a link extending between and pivotally mounted at its opposite ends on the said pivot surfaces on said movable contact blade and said actuator blade, said link retaining said movable contact blade on said fulcrum.

6. A switch comprising a flexible blade member having a mounting end with a polygonal hole therethrough, a pair of spaced parallel fulcrum legs extending outwardly from said mounting end, a pair of spaced parallel actuator legs extending outwardly from said mounting end to opposite sides of said fulcrum legs and an outer end portion joining said actuator legs outwardly of said fulcrum legs, at least one stationary contact blade having a mounting end with a polygonal hole therethrough aligned with the hole in said flexible member and a contact end extending outwardly a short distance from said mounting end and terminating intermediate the ends of said fulcrum legs, a terminal having a polygonal hole therethrough aligned with the holes in said blade and said member, insulation between said terminal and the mounting ends of said stationary contact blade and said flexible member and forming therewith a mounting stack, a polygonal tube of insulating material disposed within said stack and intimately engaging in said holes in said terminal, said blade and said member, said tube being of a height less than said stack, a single fastener passing through said tube and having head means at its opposite ends pressing against the opposite sides of the stack, at least one of said head means comprising a cup washer imposing a tensile load on said fastener and a compressive load on said stack, said fulcrum legs including transverse portions adjacent their outer ends tilted relative to said legs and defining a knife-like fulcrum edge, a movable contact blade mounted between said fulcrum legs and extending proximate to said stack and the said blade end of said stationary contact blade, said movable contact blade comprising a generally planar member having upstanding flanges intermediate the ends and adjacent the opposite sides thereof, said transverse portions of said fulcrum legs being opposed to said flanges and having longitudinally extending slots therein, said flanges being received within said slots and having recesses in the ends thereof engaging about the said knife-like fulcrum edge, whereby the movable contact blade is pivotally mounted on said fulcrum edge and effectively interlocked with said fulcrum legs, said movable contact blade having a pivot surface on a portion thereof spaced from said fulcrum surface and said outer end portion of said flexible member including a pivot surface on a portion thereof opposed to the said portion of said movable contact blade, a link extending between and pivotally mounted at its opposite ends on the said pivot surfaces on said movable contact blade and said transverse portion of said flexible member, said link retaining said movable contact blade on said fulcrum, said actuator arms being prestressed to bias said outer end portion of said flexible member in such direction as to cause said movable contact blade to be normally disengaged from said stationary contact blade, a strut pivoted on said flexible member adjacent said stack and extending therefrom to the central part of said outer end portion of said flexible member, said outer end portion having a slot in the central part thereof, said strut being received within said slot in spaced relation to the inner end of the slot and bearing exclusively on the surface of said outer end portion facing in the direction of normal bias of said actuator legs, and a wire subject to thermal expansion upon passage of electric current therethrough extending from said terminal to the outer end of said strut at the side of said flexible blade member opposite the direction of normal bias of said actuator legs, said wire normally being of a length to hold said strut and said outer end portion of said flexible member in position to cause en- 10 gagement of said movable contact blade with said stationary contact blade.

7. In a switch, a mounting stack, a pair of spaced stationary blades projecting a short distance outwardly from the stack, a flexible blade member projecting outwardly from said stack beyond said stationary blades, said member including a pair of spaced parallel flexible fulcrum legs extending outwardly beyond said stationary blades, a pair of flexible actuator legs spaced laterally outward from respective ones of said fulcrum legs and an outer end portion joining said actuator legs outwardly of said fulcrum legs, said fulcrum legs defining a fulcrum adjacent the outer ends thereof, a short movable contact blade pivoted on said fulcrum and projecting inwardly therefrom between said fulcrum legs into the space between said stationary blades and proximate to said stack, said fulcrum legs including at their outer ends transverse portions defining said fulcrum, each of said transverse portions having a longitudinal slot therein, said movable contact blade including at its opposite sides upstanding flanges fitting within the respective ones of said slots and extensions projecting beyond said fulcrum, the edges of said flanges engaging said transverse portions having recesses therein receiving said transverse portions and effectively interlocking said movable contact blade and said fulcrum legs, said movable contact blade having a pivot surface on a portion thereof spaced from said fulcrum and said outer end portion of said flexible member including a pivot surface on a portion thereof opposed to the said portion of said movable conact blade, a link extending between and pivotally mounted at its opposite ends on the said pivot surfaces on said movable contact blade and said actuator blade, said link retaining said movable contact blade on said fulcrum, said actuator legs being prestressed in a given direction normally to disengage said movable contact blade from one of said stationary blades, a terminal in said stack, a strut pivotally mounted on said flexible member adjacent said stack and extending to adjacent the outer end of said flexible member, said strut engaging said outer end portion of said flexible member solely at the surface thereof facing in said given direction, and a wire subject to thermal elongation upon passage of electric current therethrough extending from said terminal to the outer end of said strut at the side of said flexible member facing in the direction opposite said given direction, said wire normally being of a length to hold said strut and said outer end portion of said flexible member in position to cause engagement of said movable contact blade with said one stationary blade.

8. In a switch, a mounting stack, a pair of spaced stationary blades projecting a short distance outwardly from said stack, a fulcrum portion projecting outwardly from said stack beyond said stationary blades, said portion being bifurcated from inwardly of the outer ends of said stationary blades to its outer end and defining a fulcrum adjacent the outer end thereof, a short movable contact blade pivoted on said fulcrum and projecting inwardly therefrom between the bifurcations of said portions into the space between the said stationary blades and proximate to said stack, a movable actuator blade projecting outwardly from said stack beyond said fulcrum portion, said actuator blade having a window therein coextensive with the bifurcations of said fulcrum portion and terminating in outwardly spaced relation to said movable contact blade, said movable contact blade having a pivot surface on a portion thereof spaced from said fulcrum and said actuator blade including a pivot surface on a portion thereof opposed to the said portion of said movable contact blade, a link extending between and pivotally mounted at its opposite ends on the said pivot surfaces on said movable contact blade and said actuator blade, said link retaining said movable contact blade on said fulcrum, said actuator blade being prestressed in a given direction normally to disengage said movable contact blade from one of said stationary blades, a terminal in said stack, a strut pivotally mounted adjacent said stack and extending to adjacent the outer end of said actuator blade, said strut engaging the outer end portion of said actuator blade solely at the surface thereof facing in said given direction, and a wire subject to thermal elongation upon passage of electric current therethrough extending from said terminal to the outer end of said strut at the side of said actuator blade facing in the direction opposite said given direction, said wire normally being of a length to hold said strut and said outer end portion of said actuator blade in position to cause engagement of said rnovable contact blade with said one stationary blade.

9. In a switch, a stack, a pair of spaced stationary blades mounted in said stack, a flexible blade member mounted at one end in said stack and extending outwardly beyond the free ends of the stationary blades, said flexible blade member including a pair of spaced parallel actuator legs, an outer end portion joining said legs and a pair of spaced fulcrum legs disposed between said actuator legs inwardly of said end portion, said fulcrum legs extending beyond the free ends of the stationary blades and adjacent the outer ends thereof defining a fulcrum, a movable contact blade seated on said fulcrum, said movable contact blade being narrow and extending inwardly from said fulcrum between said fulcrum legs into the space between the free end portions of the stationary blades, the outer end portion of said flexible blade member being spaced outwardly from an opposed to the outer end of said movable contact blade, a link engaging at its opposite ends said end portion of said flexible blade member and said movable contact blade, said link retaining said movable contact blade on said fulcrum, said actuator legs being prestressed in a given direction normally to disengage said movable contact blade from one of said stationary blades, a terminal in said stack, a strut pivotally mounted on said flexible blade member adjacent said stack and extending to adjacent the outer end of said flexible blade member, said strut engaging said outer end portion of said flexible blade member solely at the surface thereof facing in the said given direction, and a wire subject to thermal elongation upon passage of electric current therethrough extending from said terminal to the outer end of said strut at the side of said flexible blade member facing in the direction opposite said given direction, said wire normally being of a length to hold said strut and said outer end portion of said flexible blade member in position to cause engagement of said movable contact blade with said one stationary blade.

10. In a switch, a stack, a pair of spaced stationary blades mounted in said stack, an actuator blade mounted at one end in said stack and extending outwardly beyond the free ends of the stationary blades, a fulcrum portion mounted at one end in said stack and extending at its free end beyond the free ends of the stationary blades but terminating short of the free end of said actuator blade, said fulcrum portion being bifurcated and the bifurcations thereof defining a fulcrum adjacent the outer end thereof, a movable contact blade seated on said fulcrum, said movable contact blade being narrow and extending inwardly from said fulcrum between the bifurcations of said portion into the space between the free end portions of the stationary blades, the actuator blade including a free end portion disposed outwardly of and opposed to the outer end of said movable contact blade, 2. link engaging at its opposite ends said end portion of the actuator blade and said movable contact blade, said link retaining said movable contact blade on said fulcrum, said actuator blade being prestressed in a given direction normally to disengage said movable contact blade from one of said stationary blades, a terminal in said stack, a strut pivotally mounted adjacent said stack and extending to adjacent the outer end of said actuator blade, said strut engaging the outer end portion of said actuator blade solely at the surface thereof facing in said given direction, and a wire subject to thermal elongation upon passage of electric current therethrough extending from said terminal to the outer end of said strut at the side of said actuator blade facing in the direction opposite said given direction, said wire normally being of a length to hold said strut and said actuator blade in position to cause engagement of said movable contact blade with said one stationary blade.

11. In a switch, a stack, a pair of spaced stationary blades mounted in said stack, a flexible blade member mounted at one end in said stack and extending outwardly beyond the free ends of the stationary blades, said flexible member including a pair of spaced parallel actuator legs, an outer end portion joining said legs and a pair of spaced fulcrum legs disposed between said actuator legs inwardly of said end portion, said fulcrum legs extending beyond the free ends of the stationary blades and adjacent the outer ends thereof defining a fulcrum, a movable contact blade seated on said fulcrum, said movable contact blade being narrow and extending inwardly from said fulcrum between said fulcrum legs into the space between the free end portions of the stationary blades, the outer end portion of saidflexible member being spaced outwardly from and opposed to the outer end of said movable contact blade, and a link engaging at its opposite ends said end portion of the flexible member and said movable contact blade, said link retaining said movable contact blade on said fulcrum.

12. In a switch, a pivotally movable switch blade and a fulcrum support therefor, said blade comprising a generally planar member having upstanding flanges intermediate the ends and adjacent the opposite sides thereof, said flanges at one end thereof having shallow recesses therein, said fulcrum support comprising a pair of legs each having a transverse portion opposed to the said one end of said flanges, said transverse portions having longitudinally extending slots therein, said flanges being received in said slots and said transverse portions engaging edgewise within said recesses against the said one end of said flanges, whereby the blade is pivotally mounted on said transverse portions and effectively interlocked with said fulcrum support.

13. In a switch, a pivotally movable switch blade and a fulcrum support therefor, said blade comprising a generally planar member having upstanding flanges intermediate the ends and adjacent the opposite sides thereof, said flanges at one end thereof having shallow recesses therein, said fulcrum support comprising a pair of legs spaced apart a distance approximately the same as the spacing of said flanges, said legs each having a transverse portion tilted relative to the plane of said blade and opposed to the said one end of said flanges, said transverse portions having longitudinally extending slots therein,'said flanges being received between said legs within said slots and said transverse portions engaging edgewise substantially on a knife edge within said recesses against the said one end of said flanges, whereby the blade is pivotally mounted on said transverse portions and effectively interlocked with said fulcrum support.

14. In a switch having a terminal, a stationary contact, a movable contact blade and actuating means for said blade prestressed in a given direction such as to bias said movable blade away from said stationary contact, the improvement comprising a strut pivotally mounted on a stationary portion of the switch and including a portion engaging said actuating means solely at a surface thereof facing in said given direction, and a wire subject to thermal elongation upon passage of electric current therethrough extending from said terminal to said portion of said strut at the side of said actuating means facing in the direction opposite said given direction, said wire normally being of a length to hold said strut and said actuating means in position to cause engagement of said movable contact blade with said stationary contact, said wire upon passage of electric current therethrough being subject to sutficient elongation to release said strut 2,315,867 and said actuating means. 2,338,890 References Cited in the file of this patent UNITED STATES PATENTS 3 5 1,924,639 Corcoran Aug. 29, 1933 5 2,905,780 2,184,699 Horton Dec. 26, 1939 ,9

2,277,443 Livingston Mar. 24, 1942 14 McOluer Apr. 6, 1943 Zierdt Jan. 11, 1944 Swanson Feb. 19, 1946 Vigren et a1. Nov. 6, 19 51 Wagstaif Feb. 11, 1958 Cherry Sept. 22, 1959 Jaidinger May 3, 1960 

14. IN A SWITCH HAVING A TERMINAL, A STATIONARY CONTACT, A MOVABLE CONTACT BLADE AND ACTUATING MEANS FOR SAID BLADE PRESTRESSED IN A GIVEN DIRECTION SUCH AS TO BIAS SAID MOVABLE BLADE AWAY FROM SAID STATIONARY CONTACT, THE IMPROVEMENT COMPRISING A STRUT PIVOTALLY MOUNTED ON A STATIONARY PORTION OF THE SWITCH AND INCLUDING A PORTION ENGAGING SAID ACTUATING MEANS SOLELY AT A SURFACE THEREOF FACING IN SAID GIVEN DIRECTION, AND A WIRE SUBJECT TO THERMAL ELONGATION UPON PASSAGE OF ELECTRIC CURRENT THERETHROUGH EXTENDING FROM SAID TERMINAL TO SAID PORTION OF SAID STRUT AT THE SIDE OF SAID ACTUATING MEANS FACING IN THE DIRECTION OPPOSITE SAID GIVEN DIRECTION, SAID WIRE NORMALLY BEING OF A LENGTH TO HOLD SAID STRUT AND SAID ACTUATING MEANS IN POSITION TO CAUSE ENGAGEMENT OF SAID MOVABLE CONTACT BLADE WITH SAID STATIONARY CONTACT, SAID WIRE UPON PASSAGE OF ELECTRIC CURRENT THERETHROUGH BEING SUBJECT TO SUFFICIENT ELONGATION TO RELEASE SAID STRUT AND SAID ACTUATING MEANS. 